RVFV & EHDV Flashcards
(38 cards)
1
Q
What type of virus is RVFV? What Genus does it belong to?
A
- Bunyaviruses
- Phlebovirus
2
Q
What are the characteristics of RVFV?
A
- Enveloped
- Single-stranded RNA (Group V)
- segmented genome:
- L (large) M (medium) S (small)
3
Q
How is RVFV spread? How can the virus be inactivated?
A
- Arthropod-borne (mosquitos)
- Zoonotic
- Inactivated by lipid solvents, detergents, and low pH
3
Q
How is RVFV spread? How can the virus be inactivated?
A
- Arthropod-borne (mosquitos)
- Zoonotic
- Inactivated by lipid solvents, detergents, and low pH
4
Q
What is the genomic structure of RVFV?
A
- Segmented - 11.9kb
- Large: Viral polymerase
- Medium: Glycoproteins (Gn, Gc), NSm
- Small: Nucleoprotein (N), NSs
- Ambisense RNA segment
- Relatively low genetic diversity for RNA virus
5
Q
What is the geographic spread of RFVF?
A
- Mosquito-borne zoonotic disease of domestic and wild ruminants:
- 1st reported in Kenya in early 1900s
- Endemic in tropical and subtropical regions of Africa, Madagascar, Arabian Peninsula
*
6
Q
What are the common results of epidemics/epizootics of RVFV?
A
- Acute febrile disease
- Abortion in livestock
- abortion storm
- death of young animals
- Major affected species:
- Sheep
- cattle
- goats
- influenza-like illness in humans
7
Q
Why is RVFV important?
A
- Emerging transboundary viral disease
- Reportable FAD
8
Q
When do outbreaks of RVFV occur?
A
- associated with abnormally heavy rainfalls or localized flooding
- Epidemics occur at 5-15y intervals in Africa - peaks in late rainy season, late summer
- Seasonal outbreaks in colder regions
9
Q
Why are outbreaks of RVFV associated with heavy rainfall?
A
- Transovarial transmission in mosquitoes - dormant virus in eggs in soil
- Heavy rainfall ⇢ eggs hatch, infected mosquitoes emerge
- Virus can also subclinically cycle between mosquitoes and mammalian hosts between outbreaks
- Virus is spread by movement of viremic animals and wind-borne mosquitoes
10
Q
What are the insect vectors of RVFV
A
- Mosquitoes:
- Aedes
- Anopheles
- Culex
- Other potential species including US mosquitoes
- Biting flies - mechanical vector
11
Q
Can infected animals/humans infect mosquitos with RVFV?
A
- Infected livestock - sheep, cattle, goats
- High levels of viremia
- Sufficient to infect feeding mosquitoes
- Establishes disease in environment
- Leads to large epizootic/epidemics
- High levels of viremia
- Humans can have viremia levels high enough to infect mosquitos
12
Q
What animals are the most susceptible to RVFV?
A
- Mortality 100%
- young animals (lambs, calves, kids, puppies, kittens, rodents)
- Severe illness abortion mortality
- Sheep, cattle, goats, humans
13
Q
What animals are resistant to RVFV?
A
Horses and pigs
14
Q
What is the mortality rate of RVFV in lambs/kids? Clinical signs?
A
- Very high mortality (90-100%)
- Incubation period 12-36 hours
- high fever (up to 108F)
- Listlessness
- Reluctance to move
- reduced appetite
- abdominal pain
- tachypnea
- Death within 12 hours to 3 days
15
Q
What is the mortality rate of RVFV in sheep/goats? Clinical signs?
A
- Lower mortality (20-30%)
- Incubation period: 24-72h
- Fever
- lethargy
- diarrhea
- icterus
- hematemesis
- hematochezia
- mucopurulent nasal dishcarge
- Can be subclinical
16
Q
What is the mortality rate of RVFV in calves? Clinical signs?
A
- Less susceptible than lambs (10-70% mortality)
- Clinical signs similar to lambs/kids:
- fever
- depression
- acute death
- Death within 2-8d after onset
17
Q
What is the mortality rate of RVFV in cattle? Clinical signs?
A
- Lower mortality (5-10%)
- infections are often subclinical
- Fever
- weakness
- reduced appetite
- lacrimation
- salivation
- nasal discharge
- dysgalactia
- diarrhea
- hematochezia
- icterus
18
Q
What are the clinical signs of RVFV in pregnant livestock?
A
- Abortion - may be only sign
- Abortion storm in affected herds
- Ewes/does: high rate (5-100%) seen, occurs at any stage of gestation
- Cattle: usually < 10%, can be up to 85% during outbreaks
- Aborted fetuses are usually autolyzed
19
Q
Is there a vaccine for RVFV?
A
- Modified-live Smithburn vaccine
- Not available in US
- Side effects:
- early embryonic death
- congenital CNS abnormalities
- arthrogryposis
- Abortion / stillbirth
20
Q
Who should perform the necropsy on animals with suspected RVFV?
A
trained personnel with appropriate PPE
21
Q
What gross lesions are expected in an animal with RVFV?
A
-
Hepatitis:
- Enlarged, soft, yellow, friable liver
- Irregular congested patches or petechial hemorrhages
- numerus grayish white necrotic foci
- Hemorrhage and edema of gallbladder wall and mucosa of abomasum
- Dark born intestinal contents
- Splenomegaly + lymphadenopathy with edema and petechiae
22
Q
What microscopic lesions are expected in an animal with RVFV?
A
severe and extensive hepatic necrosis
23
Q
When should RVFV be suspected?
A
When abnormally heavy rains and flooding are followed by widespread occurrence of abortions and mortality among newborn ruminants characterized by necrotic hepatitis, concurrent with influenza-like disease in people handling animals
24
How is RVFV diagnosed?
* **Reportable FAD**
* **PCR/VI**
* tissue of aborted fetuses, liver, spleen
* blood of infected animals
* **Viral antigen detection**
* ELISA, IHC, antigen staining of organ impression smears
* **Serological tests**
* Acute and convalescent samples
* IgM ELISA - detects recent infection
25
How should RVFV be managed?
* Contact authorities:
* PPE - gloves, coveralls, boots, eyewear, respirator
* Avoid contact with infected tissues/blood
* Restrict animal movement, quarantine
* Do NOT slaughter sick animals - bury or burn
* Vaccination - NOT in US
* Vector control:
* insect repellents, environmental management (standing water breeds mosquitoes)
26
How do humans become infected with RVFV?
* Readily infects people via direct contact
* Slaughter or necropsy of infected animals
* Contact with infected tissues, body fluids, aborted fetuses
* High risk: veterinarians, farm laborers, abattoir workers, butchers
* NO person-to-person transmission reported
27
What are the human clinical signs of RVFV?
* **Usually subclinical**
* Incubation period 2-6 days
* **flu-like illness** - fever, malaise, myalgia, headache, nausea, vomiting, arthralgia
* Self-limiting - recovery in 4-7 days
* **Sever Disease 1-2% of cases**
* Ocular disease (retinopathy), encephalitis, or severe hepatic lesions with hemorrhage
* Death in 10-20% of severe cases
* Overall mortality rate: ~1%
28
What family is Schmallenber virus (SBV) part of? Genus?
* Bunyaviruses
* Orthobunyavirus
29
What are the characteristics of SBV?
* Enveloped
* ssRNA viruses (Group V)
* Segmented genome
* Arthropod-borne (*Culicoides sp)*
* Domestic and wild ruminants only - **not zoonotic**
* Susceptible to common disinfectants
30
What is the history of SBV?
* Identified in 2011 - European cattle, sheep, goats, bison
* Affected dairy cow herds:
* fever, reduced appetite, reduced milk production, weight loss
* High herd morbidity (20-70%), recovery after a few days
* Sheep, goats, cattle:
* abortions and stillbirths with congenital malformations
* up to 20-50% aborted/deformed lambs in affected sheep flocks
31
How is SBV transmitted?
* Biting flies (*Culicoides sp)*
* Vertical transmission by *in utero* infection
* Direct transmission between animals NOT reported - unlikely
32
What are the clinical signs of SBC in adult sheep/goats?
* Increased abortions and congenital malformations in offspring
* Otherwise generally subclinical
33
What are the clinical signs of SBV in adult cattle?
* Can be subclinical
* Transient fever, reduced appetite, malaise, reduced milk production, diarrhea, abortion - recovery within a few days
* Lower incidence of congenital malformations than sheep
34
What Congenital malformations can SBV cause in neonates and fetuses?
* Arthrogryposis/hydranencephaly syndrome (AHS)
* Specific signs reflect stage of gestation when infected
* Stillbirth, premature birth, mummified fetuses
* Arthrogryposis, hydranencephaly, ataxia, paralysis, muscle atrophy, joint malformations, torticollis, kyphosis, scoliosis, behavioral abnormalities, blindness
35
Why is SBV important?
* FAD - Reportable
* Chance of introduction to US
36
How is SBV diagnosed?
* PCR, VI, SN Ab test, ELISA, IFA
* fetus/neonate: brain, spleen, blood, placenta, amniotic fluid, meconium
* Dam/Adult: blood
37
How is SBV controlled?
* No specific treatment
* Vector control - house pregnant animals indoors at night during critical periods to reduce exposure
* breed outside the vector season
* Inactivated vaccines - available in some countriessss
